The present invention generally relates to memory devices that use a light generated current and a method of using those devices. More particularly, the present invention relates to write once read many optical memory (WORM) devices that use avalanche breakdown to write data and a method of using those devices.
The most common forms of optical data storage are the compact disk (CD) and the digital versatile disk or digital video disk (DVD). CDs and DVDs that can be encoded one time by the user are referred to as write once read many (WORM) CDs and DVDs. DVDs are similar to CDs except that a smaller wavelength of light is used (e.g., blue instead of red) and may have data encoded on both sides of the disk. The data may be encoded or written into WORM CDs and DVDs by a laser beam. The writing of the data is slow since it is performed serially.
One type of writing is ablative writing. Ablative writing heats a material above its melting point causing a small hole. If the ablative writing process does not heat the material sufficiently, then an unstable amorphous mark is created which may vanish a few days later. Another problem is optical aberrations caused by the pressure within the optical CD or DVD. The presence of optical aberrations, unstable amorphous marks and the like are a problem for ablative WORM CDs and DVDs.
Another type of writing is phase change writing. Phase change writing rapidly heats and cools a phase change layer. A thin insulating layer is typically used in conjunction with a high power write laser to heat the phase change layer and a quenching layer is used to rapidly dissipate this heat. The insulation layer, the quenching layer and the high write power laser limit the general applicability to existing technology and increases the manufacturing cost.
Another form of data storage is programmable read only memory (PROM). PROM is a form electrically addressed memory that can be written to once by applying a voltage across a storage element to disable it. The process of disabling of elements is relatively slow because of the serial nature of PROM devices. Once formed, PROMs must be inspected to insure that their complex structure has been correctly formed. The inspection process adds time and expense to the manufacturing process. The cost of manufacture is further increased because the complex structure of PROM devices results in lower yields.
Accordingly, there is a strong need in the art for a reliable fast writing WORM device having a simple structure that may be written to in a simple manner.
An aspect of the invention provides for method of writing data to an optical storage media including providing a first voltage across a first pixel, the first pixel including a light emitting element that generates light in response to a second voltage being applied across the first pixel and illuminating the first pixel while providing the first voltage across the first pixel to induce a light induced avalanche breakdown current through the first pixel. The light induced avalanche breakdown current changes the first pixel such that the light emitting element will be prevented from generating light in response the second voltage being applied across the first pixel.
Another aspect of the invention provides for an optical storage media including a plurality of pixels, each pixel including a light emitting element capable avalanche breakdown in response to a first voltage being applied across the light emitting element and capable of generating light in response to a second voltage being applied across the light emitting element and a cathode and an anode for applying voltage to the light emitting element. The avalanche breakdown occurs when the light emitting element is illuminated while providing the first voltage across the light emitting element. The avalanche breakdown creates a current that causes a change that prevents the light emitting element from generating light in response the second voltage being applied across the light emitting element.
A further aspect of the invention provides for a method of writing data to an optical storage media including a plurality of pixels including providing a reverse bias voltage across a pixel, the pixel including an organic light emitting diode that generates light in response to a forward bias voltage being applied across the pixel and illuminating the pixel while providing the reverse bias voltage across the pixel to induce a light induced avalanche breakdown current through the pixel such that the light emitting element will be prevented from generating light in response the forward bias voltage being applied across the pixel.
A still further aspect of the invention provides for an optical storage media including a plurality of pixels, each pixel including a light emitting organic diode capable avalanche breakdown in response to a reverse bias voltage being applied across the light emitting organic diode and capable of generating light in response to a forward bias voltage being applied across the light emitting organic diode and a cathode and an anode for applying voltage to the light emitting organic diode. The avalanche breakdown occurs when the light emitting organic diode is illuminated while providing the reverse bias voltage across the light emitting organic diode. The avalanche breakdown creates a current that causes a change that prevents the light emitting organic diode from generating light in response the forward bias voltage being applied across the light emitting organic diode.
A still further aspect of the invention provides for a method of writing data to an optical storage media including providing a reverse bias voltage across a pixel, the pixel including a light emitting element and illuminating the pixel. The combination of illuminating the pixel and providing the reverse bias voltage across the pixel disables the light emitting element.
A still further aspect of the invention provides for an optical storage media including a plurality of pixels, each pixel including a light emitting element capable of being disabled in response to a first voltage being applied across the light emitting element and capable of generating light in response to a second voltage being applied across the light emitting element and a cathode and an anode for applying voltage to the light emitting element. The disabling occurs when the light emitting element is illuminated while providing the first voltage across the light emitting element and creates a current that causes a change that prevents the light emitting element from generating light in response the second voltage being applied across the light emitting element.